The link "adds to evidence that PMDD is a disorder of cellular response to estrogen and progesterone," said study researcher Dr. Peter Schmidt. He's with the National Institute of Mental Health, part of the U.S. National Institutes of Health.

"For the first time, we now have cellular evidence of abnormal signaling in cells derived from women with PMDD, and a plausible biological cause for their abnormal behavioral sensitivity to estrogen and progesterone," he said in an NIH news release.

Scientists had already known that women with the disorder are especially sensitive to changes in sex hormones, even though their hormone levels are normal.

For the new study, the researchers looked at how gene expression was controlled in white blood cells. They found a complex of genes that acts differently in women with the disorder compared to women without it.

Dr. David Goldman, of the U.S. National Institute on Alcohol Abuse and Alcoholism, worked with Schmidt on the study.

"This is a big moment for women's health, because it establishes that women with PMDD have an intrinsic difference in their molecular apparatus for response to sex hormones -- not just emotional behaviors they should be able to voluntarily control," Goldman said.